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Current transducer

Below you can find relevant Current Transducer information - the links will lead you to our Danisense Current Transducer range.

Standard Transducers

Family
Name
DT Series
Output
type
CurrentVoltage
OptionsStandardCalibration WindingStandard
Rated primary current Arms50ADT50ID
100ADT100ID
200ADT200ID
300-400A
500-1000A
1200A
2000A
3600A
5000A
7000A
Family
Name
DS Series
Output
type
CurrentVoltage
OptionsStandardCalibration WindingStandard
Rated primary current Arms50ADS50IDDS50UB-1V
DS50UB-10V
200DS200IDDS200ID-CD100
DS200ID-CD1000
DS200UB-1V
DS200UB-10V
300-400ADS300ID
DS400ID
DS300UB-1V
DS300UB-10V
DS400UB-1V
DS400UB-10V
500-1000ADS600IDDS600ID-CD100DS600UB-1V
DS600UB-10V
DS1000UB-10V
1200A
2000A
3600A
5000A
7000A
Family
Name
DM Series
Output
type
CurrentVoltage
OptionsStandardCalibration WindingStandard
Rated primary current Arms50A
200
300-400A
500-1000A
1200ADM1200IDDM1200ID-CD3000DM1200UB-1V
DM1200UB-10V
2000A
3600A
5000A
7000A
Family
Name
DL Series
Output
type
CurrentVoltage
OptionsStandardCalibration WindingStandard
Rated primary current Arms50A
200
300-400A
500-1000A
1200A
2000ADL2000IDDL2000ID-CD100
DL2000ID-CB100
DL2000UB-1V
DL2000UB-10V
3600A
5000A
7000A
Family
name
DQ Series
Output
type
Current
OptionsStandardProgramable
Rated primary current Arms50A
200
300-400A
500-1000ADQ500ID
DQ600ID
DQ640ID-B
1200A
2000A
3600A
5000A
7000A
Family NameOutput TypeOptionsRated primary current Arms
50A100A200A300-400A500-1000A1200A

DT Series


Current transducer
CurrentStandardDT50IDDT100IDDT200ID

DS Series


Current transducer
CurrentStandardDS50IDDS200IDDS300ID
DS400ID
DS600ID
Calibration WindingDS200ID-CD100
DS200ID-CD1000
DS600ID-CD100
VoltageStandardDS50UB-1V
DS50UB-10V
DS200UB-1V
DS200UB-10V
DS300UB-1V
DS300UB-10V
DS400UB-1V
DS400UB-10V
DS600UB-1V
DS600UB-10V
DS1000UB-10V

DM Series


Current transducer
CurrentStandardDM1200ID
Calibration WindingDM1200ID-CD3000
VoltageStandardDM1200UB-1V
DM1200UB-10V

DQ Series


Current transducer
CurrentStandardDQ500ID
DQ600ID
ProgramableDQ640ID-B

Special Transducers

Family NameOutput TypeOptionsRated primary current Arms
72 A300 A

DP series


Current transducer
CurrentDP50IP-B

DC Series


Current transducer
CurrentDC200IF
Family NameDP series
Output
Type
Current
Options
Rated primary current Arms72 ADP50IP-B
Family NameDC series
Output TypeCurrent
Options
Rated primary current Arms300 ADC200IF

High Current Transducers

Family NameOutput TypeOptionsRated primary current Arms
2000 A5000 A10000 A

DL Series



Current transducer
CurrentStandardDL2000ID
Calibration WindingDL2000ID-CD100
DL2000ID-CB100
VoltageStandardDL2000UB-1V
DL2000UB-10V

DR Series



DR Series
CurrentDR5000IMDR10000IM
VoltageDR5000UX-10V / 5000A
DR5000UX-10V / 7500A
DR10000UX-10V
Family
name
DR SeriesDR Series
Output
type
CurrentVoltage
Options
Rated primary current Arms5000 ADR5000IMDR5000UX-10V / 5000A
DR5000UX-10V / 7500A
10000 ADR10000IMDR10000UX – 10V

What is a current transducer?

What would we do without electricity? Nothing! This energy is everywhere and the ongoing energy transition and decarbonization of our industry is pulling for even more electrification in all our daily activities like e-mobility for example. Like any physical quantities if you don’t measure it, you can’t manage it! Indeed in any processes the measurement is critical to monitor, to meter and to control the system and to do it a current transducer is needed. Basically a current transducer is a device converting the current signal we wanted to measure, called “primary” current, into another signal, called “secondary” current or voltage, usable by electronic control board or instruments. As the primary current can be different (AC or DC, few mA to kA, isolated or not…), there is a large diversity of current transducers using different technologies described below.

What are the different types of current transducers?

This chapter is describing the most popular current transducer technologies summarized in the diagram below. Basically there are two main families using either 1) the Ohm’s law (V = R I) also called “shunt” or 2) the Ampere’s law (I = ∮H ds) using the magnetic field to measure the current.

Current transducer technologies diagram

The choice of the current transducer technology is depending on the applications. The table below compares the performances between these different technologies for the main measurement parameters.

current transducer performance table

Measuring shunt

When you were student and if you remember your courses of physics, the shunt is using the famous formula V = R x I. Basically the shunt is made with a material which the resistor value is known. When a current is passing through the shunt, the resulting voltage is proportional to this current by the R factor. By using this principle we can achieve a good accuracy for AC and DC current with a small size. However, when the current is increasing (typically above 100A) it generates immense heat and additionally, shunts are not isolated which could be an issue for some applications with high voltages.   

 

Hall effect current transducers

First of all, a Hall effect current transducer is using a Hall probe. Basically, when you power this probe and you apply a transverse magnetic field perpendicular to the surface, it will generate a voltage proportional to this magnetic field strength. As we know from Ampere’s law, a current passing into a conductor generates a magnetic field. Therefore if we can concentrate this magnetic field on one specific point where the Hall probe is positioned, then we can measure the current. This is exactly what a Hall current transducer principle is doing by using a magnetic core concentrating the field in the air gap where the probe is placed. Therefore the voltage output is proportional to the magnetic field which is proportional to the primary current. The performances of the current transducer, like linearity or temperature offset drift, are strongly depending on the performances of the Hall probe in what we called Open loop configuration. To reduce this influence, the Closed-loop principle has been introduced. The idea is to add a secondary winding to “reinject” an opposite proportional current to compensate for the primary current. In that case, the Hall probe always works around zero magnetic fields avoiding linearity inaccuracy. Basically, the performances of such Hall effect current transducers are good and most importantly isolated. However, the Hall effect probe imperfection and the presence of the air gap increases the sensitivity to the external fields making these transducers not ideal to be used for high-end applications like lab’s power measurement or MRI application.

Magneto-resistor (AMR or GMR)

Basically, the current transducer construction is the same as for the Hall effect current transducer. However, the Hall probe is replaced by a Magneto-resistor probe in which the resistor value changes proportionally to the magnetic field. As the Magneto-resistor is better in terms of offset temperature drift these current transducers are usually more accurate than the Hall effect but with the same EMC sensitivity limitation due to the air gap.

Flux Gate current transducer

In general, the flux gate principle is to use an excited magnetic material coil as a probe. Thanks to a  saturation/desaturation cycle and signal processing, this coil is able to measure the magnetic field proportionally. From that multiple options are possible to design a current transducer. It can simply replace a Hall effect probe in the air gap or the coil could have the shape of a tore. For this second option, the current transducer can achieve really high accuracy (few ppm) and a strong EMC robustness. For more detail we invite you to read the detailed article on the flux gate principle.   

How does a current transducer work?

Measuring the electrical current directly is quite a challenging task. This is often simplified by measuring the side-effects of the passing current e.g. measuring the voltage drop created across a resistive shunt (Ohm’s law) or measuring the magnetic field surrounding the primary conductor (Ampere’s law). 

Current measurement using a resistive shunt is quite straightforward, but requires that the user interrupts the primary circuit to insert the shunt, provides proper cooling of the shunt, or at least does proper shunt sizing for the required current range, with the downside of having a current measurement signal which is not isolated from potentially hazardous primary voltage levels.

Current measurement by using the generated magnetic field has the advantage of being a non-contact i.e. isolated current measurement so that the primary circuit does not need to be interrupted with the insertion of a lossy component like the resistive shunt. The magnetic field created by a passing current through a primary conductor is proportional to the applied current and therefore carries the information about the current amplitude. The way the measured magnetic field is transformed into information about the current amplitude will depend on the measurement principle (link to “What are the different types of current transducers”), but the common advantage is that current measurement is completely isolated from the primary power circuit which often makes the important task of control and protection of complex electrical systems easier to deal with.

 

Current transducer working principle?

By now the interested reader has learned that current transducers measuring the magnetic field around an energized primary conductor can use different kinds of measuring probes to sense the magnetic field e.g. Hall-effect, Flux-gate, Magneto-resistive probe, etc. In the simplest implementation of a current transducer using a magnetic field probe called “open-loop”, the output of the aforementioned probe is used directly as an indication of the measured primary current and although the two are proportional, the accuracy and linearity of the current transducer when measuring small or large currents (or both) can be inferior. This nonlinearity can be the result of a poor magnetic probe design, but it is quite often worsened by driving the magnetic core of the current transducer quite far from the origin of the hysteretic B-H characteristic or even deep in magnetic saturation. Another two parameters that can be negatively affected in the open-loop implementation of the current transducer is the stability and the drift of the current measurement (both in terms of time i.e. long-term stability and operational temperature). Open-loop current transducers often have a voltage output representing the measured primary current with a certain defined ratio specified in the datasheet (V/A).

The problems of the open-loop current transducers are alleviated by implementing a closed-loop current transducer principle where the output of the magnetic probe is used as a feedback signal to drive a secondary current through a compensation winding inserted around the same current transducer core. The goal for the current transducer closed control loop here is that the magnetic Ampere-turns of the secondary current passing in the compensation winding ideally compensate the primary Ampere-turns and nullify the magnetic field, so that both the magnetic probes and the magnetic core of the current transducer operate in zero-flux i.e. measured magnetic field is zero. Immediate advantages of the closed-loop approach is that the most important performance parameters of a current transducer like accuracy, linearity, drift and stability are improved by far when the magnetic probe and the CT core are operated at the origin of the B-H curve. Closed-loop current transducers deliver naturally a secondary current because of the explained operating principle and the scaling ratio is specified in the datasheet (A/A). For easier interfacing with control systems, closed-loop current transducers are quite often equipped with an integrated high-precision burden resistor which transforms the secondary current into an appropriate voltage signal which represents the measured primary current with a certain defined ratio specified in the datasheet (V/A).

 

Current transducer installation?

Before performing any current transducer installation it is recommended to check that the expected maximum primary current and voltage levels are well within the specifications of the selected current transducer. During installation make sure that the magnetic field conditions around the primary conductor are as uniform as possible – this often means that return conductors are either:

  1. placed very far from the transducer, 
  2. comply with the busbar no-return zone specified for the specific current transducer, or
  3. return busbar is split in several returns placed symmetrically around the current transducer and still returned as far as possible from the current transducer housing

 

On current transducers with metal housing, it is recommended to perform grounding of the housing by removing some of the paint at the mounting feet and inserting a bolt to the mounting chassis. This will make sure that any primary induced, capacitively coupled noise is diverted into the chassis without affecting the measured current signal.

When using oscilloscopes and other measurement equipment having grounded input terminals it is important to avoid making ground loops that can give rise to short-circuit currents through the terminals of the current transducer which can effectively damage or degrade performance.

 

Dc current transducer

Not every current measurement principle based on Ampere’s law can measure DC currents. For example, the inductive current transducer and Rogowski coil are relying on the magnetic induction of current and voltage in the coil due to alternating / AC magnetic field and are effectively unable to measure DC currents.

Magnetic probes which are capable of sensing DC magnetic fields, like e.g. Hall-effect, Flux-gate, and Magneto-resistive probe can be used for building DC current transducers (often called DCCTs). Both open-loop and closed-loop implementations are possible, but the application of a strong DC magnetic field in an open-loop CT can pre-magnetize the magnetic core in a way that the measurement performance for AC currents is significantly affected taking into consideration the non-linear B-H curve of the common